The present invention relates to a device and method for lacquering or coating of plates or disks by means of an open channel and, in particular, by means of an open channel that is narrowed to a capillary slot, especially for coating glass plates for LCD production.
The present invention furthermore relates to a device and method for coating of semiconductor substrates in two steps. In the first step the coating medium or lacquer is applied preferably with a capillary slot that is filled with the coating medium or lacquer and across which the substrate, with the surface to be coated facing downwardly, is guided. In the second step, the lacquer layer thickness is made more uniform and thinner in a spinning operation with the surface to be coated facing downwardly.
In the field of thin layer technology and semiconductor manufacture, especially for the production of LCD monitors, masks for semi-conductor manufacture, semi-conductor or ceramic substrates etc., the following problem is often encountered: Rectangular or round plates must be provided with a uniform layer of lacquer or other initially liquid media for color filters or special protective layers. With commonly known devices the plates are horizontally attached to a turntable. To the center point of the plate a certain amount of lacquer or liquid is dripped from above with a nozzle. Then the turntable is rotated. Due to centrifugal forces the liquid is distributed on the substrate during rotation. A large portion of the liquid is spun across the rim of the plate. The uniformness of the layer thickness that is to be achieved with this process depends on the magnitude of the rotation acceleration and speed.
Difficulties with respect to the uniformness of the lacquer thickness on rectangular plates result with the known processes especially in the area of the corners of the plate. In these areas commonly strips of greater or lesser lacquer thickness are observed which are concentric to the center of the substrate. This causes a substantial reduction in the uniformness of the lacquer thickness.
In order to collect the lacquer which is spun across the rim of the substrate, and also for protecting the lacquering station, such lacquering turntables are commonly mounted within some form of a container. It cannot be prevented that lacquer stains are also deposited on the lateral areas of the substrate. This is disadvantageous for the further processing of the substrate. Another disadvantage of the known method is that more than 90% of the lacquer used is spun over the rim of the plate. This excess lacquer cannot be reused and is thus lost. Furthermore, the entire construction and the drive of the turntable are complicated and expensive.
From German Offenlegungsschrift 40 21 621 an improvement of this lacquering and coating process is known. Here, the liquid is sprayed in the form of a flood onto the plate with a porous tube. It may be disadvantageous for the coating process that the liquid is altered in certain properties, for example, solvent content and viscosity, by the spraying process and the corresponding pumping action. Furthermore, it is required that the flow conditions are maintained constant in order to be able to achieve the uniformness of the layer thickness required for various applications.
It is therefore an object of the present invention to improve the known lacquering and coating processes and devices with respect to the aforementioned criteria and to achieve for the process of lacquering of semi-conductor substrates the required high uniformness of the lacquer layer thickness.